That tiger died of cancer a number of years ago. The Downs Syndrome thing is a little dubious because that only affects humans & chimps, but no doubt he was hella inbred.
White tigers aren't some precious species, it's a freak mutation that without human intervention would happen extremely rarely. They aren't naturally occurring, just bred (and inbred and further inbred) with that mutation for human vanity - Vegas shows, unscrupulous zoos, etc. The genetics that makes them white also makes them have all sorts of other defects. Humans are stupid assholes sometimes.
Here's a decent write-up on why white tigers should go off into the evolutionary sunset:
http://www.slate.com/articles/health...rrelevant.html
And no WHP, it has nothing to do with vaccines.